9:00 AM - 9:15 AM
[MIS22-01] Reexamination of the hypocenter and magnitude of two damaging earthquakes of 1767
Keywords:historical earthquake
We reexamineed the epicenter location and scale of two damaging earthquakes that occurred on May 4, 1767 and October 22, 1767. We have examined the microfilmed "Takano Family Records" to discover new felt records that are not included in the existing archives and to identify the points where the records were made. The "Takano Family Records" were recorded mainly in Aoba-ku, Sendai City and Hirasawa, Zao-machi. In addition, we were able to obtain damage records in Hirasawa for these two earthquakes, which are not included in the existing archives, and felt records before and after the earthquakes. This discovery made it possible to examine the number of felt records after these two earthquakes. Therefore, we reexamined the hypocenter location and magnitude of these two earthquakes based on the distribution of damage and felt records as well as the number of felt records after the earthquakes.
The number of post-earthquake felt records after the earthquake on May 4, 1767 was low, while the number of felt records after the earthquake on October 22, 1767 was high.
Considering the distribution of felt records and the number of felt records after the earthquake, the May earthquake resembles the 1937 off Miyagi Prefecture earthquake with a small number of aftershocks, which has been called the "Kinkasan-oki type" in previous studies. The examination of observation of recent earthquakes and prediction of seismic intensity from attenuation equation indicate that an intra-plate earthquake of about M6.6 or a plate boundary earthquake of about M7.1 can explain all the damage. The October earthquake is similar to the 1938 Fukushima earthquake proposed in the previous study, which can explain the damage and the number of felt records after the earthquake.
The number of post-earthquake felt records after the earthquake on May 4, 1767 was low, while the number of felt records after the earthquake on October 22, 1767 was high.
Considering the distribution of felt records and the number of felt records after the earthquake, the May earthquake resembles the 1937 off Miyagi Prefecture earthquake with a small number of aftershocks, which has been called the "Kinkasan-oki type" in previous studies. The examination of observation of recent earthquakes and prediction of seismic intensity from attenuation equation indicate that an intra-plate earthquake of about M6.6 or a plate boundary earthquake of about M7.1 can explain all the damage. The October earthquake is similar to the 1938 Fukushima earthquake proposed in the previous study, which can explain the damage and the number of felt records after the earthquake.